(CNN) — The father who lost track of his autistic son during a visit to a Gastonia, North Carolina, park said Wednesday he’s overwhelmed with guilt as the search for the boy enters day five.

“Everybody looks at you as a monster, and I regretted it since the moment it happened,” Ian Ritch told “Good Morning America.”

Ritch said he had his eyes on young Maddox, but the 6-year-old suddenly dropped out of view Saturday. He wishes he’d never let him get so far away, he said. A police spokeswoman has said Maddox took off running during a walk around the lake.

“It’s hard to sleep. I feel guilty because I can go to a house and lay down on the bed,” the father said, “and he’s out there in the woods sleeping on the ground and that’s very upsetting.”

The father’s interview comes a day after Maddox’s mother made a tearful plea at a press conference and the FBI announced a $10,000 reward for information that leads authorities to Maddox.

‘I took off running after him’

Ritch later told reporters he and a friend were walking with Maddox when his son started running, possibly triggered by a jogger who passed by.

“He initially took off, just a little ways, maybe 25, 30 feet from me, and then he went to a major sprint after that. And that’s whenever I took off running after him,” he said.

Ritch said his son likes the outdoors and he “was giving him just a little leeway, freedom.”

He said his son often runs ahead of him, but would usually slow down and stop to give his father time to catch up.

“I couldn’t catch up with him. I feel guilt for letting him get so far ahead of me before I started running after him,” Ritch said.

Ritch said he has diabetes and neuropathy in his feet, which causes a tingling feeling or numbness, and has some trouble running.

Ritch said that the friend who was with them and some park staff members helped him look for Maddox before authorities were contacted. At that time, Ritch said, he was still optimistic.

“I felt like we could’ve found him and there was no reason to call the police until that time period. Then it got scary,” he said.

‘Continue praying for him’

Complicating the search is that Maddox is nonverbal. Hoping the youngster would reply to his parents’ voices, police have pumped prerecorded messages into Rankin Lake Park, where the boy disappeared during a Saturday afternoon visit with his dad and an unidentified adult.

Chasing more than 150 leads, local, state and federal authorities have employed dogs, drones, sonar and infrared in the search for the boy. They’ve also partially drained the 80-acre lake so they can better see its shoreline. Gastonia SWAT teams have searched the lake and nearby waterways on kayaks.

Investigators have reached out to local businesses to see if they have any useful surveillance video, and Gastonia police Chief Robert Helton says police are looking to speak with an unidentified jogger who was in the park at the time and a photographer whom witnesses saw taking photos of children dressed in Dr. Seuss costumes.

“No piece of information is too small. Something you may think is insignificant could be helpful to our case,” the chief has said.

On Tuesday, Carrie Ritch told reporters her son has a contagious smile and laugh. He loves the park, bouncy balls and his teddy bear. She urged anyone who might have seen Maddox to call authorities.

“Continue praying for him because I just want my baby home, please, whatever you can do,” she said. “Maddox is my whole world and my reason for living. He’s mama’s boy.”

Police said Maddox is 4 feet tall and weighs 45 pounds. He has blond hair and blue eyes. Maddox was last seen wearing an orange T-shirt with the words “I am the man,” along with black shorts and closed-toe sandals.

There were many children in the park Saturday, including other blond boys wearing orange T-shirts, Helton said.